The present invention relates to apparatus and methods for inserting an intraocular lens through a small incision into an eye. More particularly, the invention relates to such apparatus and methods wherein insertion of the lens is accomplished with minimum potential for damage to the lens.
An intraocular lens (IOL) is implanted in the eye, for example, as a replacement for the natural crystalline lens after cataract surgery or to alter the optical properties of (provide vision correction to) an eye in which the natural lens remains. IOLs often include an optic, and preferably at least one flexible fixation member or haptic, which extends from the optic and becomes affixed in the eye to secure the lens in position. The optic normally includes an optically clear lens. Implantation of such IOLs into the eye often involves making an incision in the eye. Making the incision as small as possible reduces trauma and speeds healing.
IOLs are known which are foldable (deformable) so that the IOL can be inserted into the eye through an incision smaller than the diameter of the lens.
Some of the most generally accepted insertion apparatus employ a hollow insertion tube having a diameter which permits the folded IOL to pass freely through the tube without permanent deformation. In these generally accepted apparatus, the insertion tube is held in a handpiece which is coupled to a plunger rod. The plunger rod is moved distally through the insertion tube to urge the IOL to pass through the tube and into the eye.
Several disadvantages are apparent in such insertion devices. For example, pushing, without trapping or holding, the IOL through and out of the hollow space defined by the tube can cause the IOL to be released from the insertion device without precise control, so that the released IOL may damage the eye and/or may be mispositioned in the eye. In addition, the rod may scratch and/or even tear the optic. Alternatively, the trailing haptic may become wedged between the rod and the plunger tip, resulting in permanent deformation of the haptic.
Various plunger tip configurations have been devised to minimize the potential for scratching and/or tearing the optic of an IOL. In U.S. Pat. No. 5,735,858, for instance, Makker et al. disclose a tip formed of an elastomeric silicone polymer composition which is softer and more elastic than the plunger rod. The tip has a distally tapered configuration which allows the tip to enter a fold of the folded IOL more effectively and efficiently than prior art tips, and to become held or trapped by the folded IOL. This allows the IOL to be carried and/or pulled, rather than pushed, by the rod/tip combination, giving a surgeon more control of the movement of the IOL through the hollow passage of the insertion tube and the release of the IOL into the eye. Also, because the proximal end of the tip can have a relatively large cross-sectional area, the rod itself can have a reduced cross-sectional area, thus minimizing the tendency of the rod to damage the lens.
The soft-tip plunger disclosed by Makker et al. is particularly suitable for use with IOLs having optics made of elastomeric silicone polymeric materials. In recent years, however, lenses having optics made of acrylic-based polymeric materials have increased in popularity, partly due to their tendency to regain their original configuration relatively slowly after being inserted in an eye in a folded condition. This delayed unfolding allows the surgeon more time to properly position the IOL in the eye after insertion so that controlled release of the IOLs from the inserter is somewhat less important.
IOLs having optics made of acrylic-based material are more susceptible to scratching and other types of damage than IOLs having optics made of silicon-based materials. In addition, acrylic materials tend to be more adherent, which increases the likelihood that a folded lens will stick to the a wall of the injector tube bore, allowing the plunger tip to advance without advancing the IOL. As a result, even when very soft tip materials are used, insertion apparatus of the type disclosed by Makker at al., which introduce at least a portion of the tip into a fold of the folded IOL, are less appropriate for use with acrylic lenses than with silicone lenses. Still another disadvantage of acrylic IOLs is their decreased flexibility relative to silicon IOLs. Because acrylic IOLs can not be folded as compactly as silicon IOLs, injectors for acrylic IOLs must be provided with larger diameter bores. The larger bores require larger diameter tips, which in turn require larger incisions in the patient""s eye.
U.S. Pat. No. 6,010,510 to Brown et al. discloses an injector designed to optimize performance with soft acrylic IOLs. Specifically, the plunger of the Brown et al. injector has a blunt, rounded tip offset from the centerline of the plunger tod. The offset tip assures that the tip is biased downward against the bottom of the cartridge bore, thus exerting constant pressure against the wall of the bore. This arrangement helps prevent the tip from riding up over the IOL and being folded within the IOL.
A potential disadvantage of the plunger design disclosed by Brown et al. is that the constant pressure exerted on the wall of the bore by the tip of the plunger results in frictional forces which the surgeon must overcome by exerting more opposing force on the plunger than would be required if there were a clearance between the plunger tip and the wall. The possibility of damage to the IOL, the wall of the cartridge, or even the IOL recipient""s eye may be increased as a result of this additional force.
It would therefore be advantageous to provide IOL insertion apparatus and methods which facilitate the insertion of the IOL in the eye in an easy, effective and controlled manner while avoiding damage to the IOL and undue trauma to the patient.
New apparatus for inserting IOLs and methods for inserting IOLs have been discovered. The present apparatus and methods address one or more of the concerns of the prior art systems, such as those noted above. The present apparatus enable the surgeon to advance the plunger of an insertion apparatus through the passage of a closed IOL cartridge with minimal force, thus reducing the risk of damaging the IOL, the IOL cartridge, or the recipient""s eye. The present invention is straightforward, easy to produce and practice, and involves little or no modification of surgical techniques. In other words, surgeons need not learn a different surgical procedure for inserting an IOL into the eye, nor does the IOL need to be modified to accommodate the present apparatus and methods.
In one broad aspect, the present invention comprises apparatus for inserting IOLs into an eye which include a tube, such as an insertion tube or cartridge, defining a hollow passage, for example, through at least a portion of which a folded IOL can be moved. This tube has an ejection port or opening, preferably at the distal end of the tube, from which the IOL is passed for insertion into an eye. An injector rod is also included and is longitudinally or axially movable within the hollow passage of the tube. The distal segment of the rod is adapted to urge the folded IOL distally through the passage, for example, by contacting the folded IOL as the distal segment of the rod passes distally in the passage. A guide assembly is provided for directing the distal segment of the rod radially outwardly, toward the bottom of hollow passage, as it progresses along the tube. This deflection of the tip of the rod toward the bottom of the passage ensures that the rod contacts a proximal edge, rather than a fold, of the folded IOL, thus reducing the likelihood that the tip will bypass or damage the IOL, and allowing less volume inside the cartridge. Further, the guide assembly allows a certain amount of xe2x80x9cplayxe2x80x9d so that the rod tip makes minimal, if any, initial contact with the passage wall, and exerts little or no pressure on the wall.
In one embodiment, the guide assembly comprises a projection such as a guide pin, depending from an inner wall of the injector handpiece and cooperating with an outer surface of the injector rod to direct the distal tip of the rod radially outwardly. In a particularly useful embodiment, at least a portion of the proximal end of the rod is tapered to allow the tip to rise gradually after contacting the proximal edge of the IOL. This prevents the tip from scraping the bottom edge wall of the injector cartridge, and is especially desirable in cases where the cartridge has a distally tapered ejection port.
In another broad aspect of the invention, a method of preparing an IOL for insertion into an eye is provided. The method comprises the steps of:
placing an intraocular lens in a folded condition in an insertion apparatus having a tube defining a hollow passage having an ejection opening, and an injector rod longitudinally movable within the hollow portion of the tube, the injector rod having a distal tip;
advancing the injector rod distally and radially outwardly toward a wall of the hollow passage to allow the distal tip of the injector rod to contact a proximal edge of the folded intraocular lens; and
continuing to advance the injector rod distally to urge the folded intraocular lens toward the ejection opening of the apparatus.
The step of continuing to advance the injector rod distally may also include a step of allowing the tip of the rod to return upwardly, away from the wall of the hollow passage, after contacting the proximal edge of the IOL.
Insertion apparatus as disclosed elsewhere herein are particularly useful in practicing the present methods.
Each and every feature described herein, and each and every combination of two or more of such features, is included within the scope of the present invention provided that the features included in such a combination are not mutually inconsistent.
These and other aspects of the present invention will become apparent in the following detailed description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numerals.